1. Field of the Invention
The present invention relates to the field of area detection methods of the original to be applied to such copying machines as the so-called intelligent copying machine and in particular, a method for detecting an area by optically reading the mark of a specific color entered on the original.
2. Description of the Prior Art
An intelligent copying machine is a copying machine which performs specific copying processing in only a specified area of the original, such as erasure, extraction, color copying, enlargement, and reduction.
In a prior art intelligent copying machine as shown in FIG. 1, cursors 2, 3 and cursors 4, 5 are typically provided in the vertical and the horizontal directions of a platen 1 respectively, and by shifting these cursors an area A shown in diagonal lines is designated on an original 7. The area A is detected based on electric signals showing the shifted positions of the cursors 2 to 5.
The shifting of the cursors 2 to 5 is performed with the side to be copied of the original placed on the platen 1, i.e., in a state where the content of the original is not visible to an operator. Accordingly, considerable time and effort is required for the designation of the area, and yet the operator is likely to designate an incorrect area different from the intended one.
A method has been proposed in a conventional intelligent copying machine wherein, as shown in FIG. 2, an area A' of the original 7 encircled by a mark 8 of a specific color is detectected by scanning the original 7 with a photosensor sensitive only to the specific color of the mark 8. More particularly, points p and p' in which p is a point at which the photosensor detected the mark 8 the first time (start point) and p' is a point the photosensor detected the mark 8 the next time (end point) are detected is each scan line, length and position of section p-p' are measured and the entire area A is detected based on the data of these sections.
According to this area detection method, however, when the photosensor scan is performed at the top or bottom end of the mark 8, the contact point of the scan line with the mark 8 is taken as the start point p of the section and the end of the scan line as the end point p' of the section, causing a detection error of the area A'.